Terraformer alert: Habitable planets orbit 1/3 of Sun-like stars

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The Kepler orbiting observatory research team found more than 1,200 exoplanets in its first 136 days of operation. Using their data, other researchers are now calculating that there may be many, many more—so many, in fact, that we might find habitable worlds around one-third of all Sun-like stars.

The Kepler research team's findings, released earlier this year, revealed evidence of 1,235 exoplanets found after viewing some 150,000 target stars. That's a big haul for just a fraction of a year's work, but it's only a tiny portion of the universe.

Using the Kepler data, other researchers have begun statistical analysis in an effort to extrapolate just how many exoplanets might be habitable. The answer: quite a few.

Wesley Traub of the California Institute of Technology revealed the results of his own statistical study on Tuesday. Using the positions of the Kepler exoplanets relative to their stars, he was able to develop a method for formulating just how many of those stars might have planets orbiting them that we can live on. From MIT's Technology Review:

"Traub says that mid-size planets are just as likely to be found around faint stars and bright ones. By contrast, far fewer small planets show up around faint stars. That's almost certainly because small planets are more difficult for Kepler to see.

"It's also easier for Kepler to see planets that are closer to their stars because it looks for the tiny changes in brightness that these transits cause. That's why almost a third of all Kepler's detections orbit their star in less than 42 days. For the most part, these planets orbit too closely to be in the habitable zone.

"What interests most astronomers is how many exoplanets orbit at a greater distance, inside the habitable zone. Most of these planets are too far away from their stars to have been picked up by Kepler yet. But Traub says his data analysis provides a way to work out how many there ought to be.

"That's because he's found a power law that describes how the number of stars with a given orbital period. So all he has to do is assume a longer orbital period equivalent to being in the habitable zone to work out how many planets there ought to be at this distance."

The result: About one-third of stars classified F, G or K (all similar to our Sun) will likely have at least one "terrestrial, habitable-zone planet."

If Traub is right, that's a lot of potential new Earths floating around out there.